1. Field of the Invention
The present invention relates to a liquid injection device of a multi-function type which allows for the selection of, when two or more kinds of sample solutions are injected into an eluant for example in a flow injection analysis, etc., a mode in which a plurality of sample solutions are to be injected, flow passages through which the sample solutions are fed or change-over of the flow passages.
In general, the liquid chromatography or the flow injection analysis, which are known as methods used for the analysis of certain chemical substances in a sample solution, involves injecting the sample solution into the flow of an eluant to separate or analyze the substances in a system under a rather high pressure. Therefore the injection of the sample solution is conventionally performed using a liquid injection device of a pressure-resistant type.
2. Description of the Prior Art
FIG. 1(A) is an example schematically showing a typical system of liquid injection, in a liquid chromatography wherein a known hexagonal valve 4 is used as the liquid injection device.
An outline of such a liquid injection system shall be explained. An eluant supplied to a passage 3 from an eluant tank 1 by a pump 2 normally goes through one of the paths of the hexagonal valve 4 which is in a connected relationship with the passage 3 as shown by the solid line in the drawing, is sent through a passage 5 and a resin filled column 6, and then finally to a detector 7. On the other hand a liquid supply loop 8 serving as a pipe path (which is generally made of a tube externally mounted on the valve and is simply called a loop, thus hereinafter it will be referred to as a loop) is connected to two other paths within the hexagonal valve 4, and a sample solution is sucked out of the vessel 9 by a pump 10 and thus fills the loop. The paths within the hexagonal valve 4 change over to a position as shown by the broken lines in the drawing for the purpose of injecting the sample solution as a "plug flow" into the flow of the eluant, so that the resin within the column 6 can make the prescribed separations based on the difference in affinity between the resin in the column 6 and each chemical substance in the sample solution An analysis is then made at the detector.
Here, the above-mentioned hexagonal valve 4 comprises a stator (a fixed body) and a rotor (a rotating body) arranged in surface contact with one another. The stator has a total of six small openings each at every 60.degree. rotated position thereof. The rotor has three grooves each connecting two of six small adjacent openings, so that the connection of two adjacent openings changes each time the rotor rotates 60.degree. as shown in the drawing. By a simple structure, a loop filling mode of the sample solution and an injection mode of a predetermined amount of the sample solution into the eluant can be secured by a rotating operation of the rotor. This valve system has been in wide use.
Also, FIG. 1(B) shows a typical system used in a case when a plurality of columns are selectively used in a liquid chromatography. An outline thereof is such that an eluant sent from an eluant tank 1 passes through the passages formed by the grooves connecting the opening as shown by the solid lines in hexagonal valves 11 and 13 and is sent to the detector 7. Therefore, in a normal condition, a sample solution injected into the eluant is separated by a column 14. However, when the passages within the hexagonal valves 11 and 13 change over as shown by the broken lines in the drawing, the specimen is separated by a column 12.
Both the flow injection analysis method and the liquid chromatography are widely used for analytical purposes. With regards to the flow injection analysis method, the reaction products resulting from the reaction of reagents with specific elements or substances in the sample solution are measured by a colorimeter or an ionic electrode, etc. This may be achieved by replacing the eluant in the liquid injection system shown in FIG. 1(A) with a reagent solution and by omitting the column 6.
As far as the liquid chromatography is concerned, the increasing requirements are such that specific chemical substances in a sample solution are analysed by utilizing the advantages resulting from the separation and the reaction as in a pre-column method or a post-column method.
Also, for the flow injection analysis method, a column is not used and only reactions between a sample solution and the reagents are used. Methods by which reactions within a flow can be advantageously performed through control of the reaction or diversification of reaction analysis are becoming very important subjects in this field.
However, in the above-mentioned liquid injection device or the passage change-over device based on a hexagonal valve or valves, the number of sample solutions which can be introduced into the liquid injection device is only one. Therefore, the injections cannot be directed into a flow of eluants having different formulations, such as sample solutions and reagents. Also in the above passage change-over device, the number of passages which can be changed over is only two, and therefore, the selection of a number of passages cannot be achieved. Thus, the conventional device of the type mentioned above lacks an important function. Also, as a method for injecting predetermined amounts of sample solutions and reagents into a flow of an eluant, for example, a method as disclosed in the Japanese Patent Laid-Open Application No. Sho 58-87464 has been proposed. The Patent Laid-Open Application discloses a method for the injection of a so-called "merging-zone type" in which a sample solution S and a reagent R are mixed together between eluants T as shown in FIG. 2(A) using two hexagonal valves, and a method for the injection of a so-called "sandwich type" in which a sample solution S is sandwiched between the reagents R as shown in FIG. 2(B). Concerning the former method for the injection of a "merging zone type": while it has an advantage that a satisfactory contact can be secured between the reagent and the sample solution, thus saving the reagent, two sets of hexagonal valves and two pumps therefor are needed. It has thus been pointed out that the device has a problem that a complete synchronization is difficult to achieve between the liquid sending state and the change-over timing of the hexagonal valves, and therefore an adverse influence over the accuracy of the analysis is unavoidable. Further, while both of the methods can simultaneously inject the sample solution and the reagent into the flow of an eluant, this function is the only one these methods can achieve, if not modified. Accordingly, they are limited in their applications.
Also, when a plurality of sample solutions of different types are to be injected into the flow of an eluant, different modes of injection for a plurality of sample solutions by the rotation of the rotor only cannot be achieved selectively. For example, it is impossible
(a) to select any one of the plurality of sample solutions for injection; PA1 (b) to selectively carry out the simultaneous injection of a plurality of sample solutions or the injection of only a portion of said plurality of sample solutions; and PA1 (c) to selectively change over the order of injection for a plurality of sample solutions, between a normal order and a reverse order. PA1 (a) selecting any one of a plurality of sample solutions and injecting the selected one; PA1 (b) selectively carrying out the simultaneous injection of a plurality of sample solutions or the injection of only a portion of said plurality of sample solutions; and PA1 (c) selectively changing over the order of injection for a plurality of sample solutions between a normal order and a reverse order.
Thus, they can have only a limited range of application.